In a system where a scattered wave is used as a direct carrier wave between a base station and a terminal, there is known a conventional technology, which may also be called a “Direction Divide Duplex (DDD).” In this technology, by using a difference in directionality between an electromagnetic wave leaving the base station and an electromagnetic wave entering the base station, with use of a circulator, a transmitted wave and a received wave are equivalently duplicated. This technology is disclosed in RFID Handbook 2 nd edition, Klaus Finkenzeller, Translated by Software Engineering Laboratory, The Nikkan Kogyo Shimbun, Ltd., page 45, May 2004.